Pain Measurement: Level 2 MegaPain In Second Molar

9. February 2016
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The medical world has increasingly come to rely on computerised technology. Nevertheless, there are complaints that evade almost every technological analysis. A variety of strategies is being used to try and make pain measurable – with surprisingly good results.

When it comes to pain medication, doctor and nurse still make judgement according to subjective statements from patients – sometimes by way of a standardised questionnaire. When it comes to law and justice in court, functional magnetic resonance has come into use here and there. Its value however has still been insufficiently verified by studies and is too complicated for use on the patient in his or her bed [Paywall].

Pain signs under influence

And so it always depends a bit on the environment and the attending physician, as to whether a patient in a dimmed state of consciousness gets an overdose of painkillers, or has to clench his or her teeth when the dose is too low, or whether the person responsible for managing the patient’s pain is able to assess the patient’s data properly. Things are especially difficult with smaller children or with adults who have problems in written and oral communication.

Although there do indeed in guidelines exist indications of possible parameters associated with degrees of pain, anybody who goes looking for studies on this type of evidence usually has only very limited success. Sweating and the resulting reduction in conductivity of the skin may indicate pain, however according to various studies [Paywall] it does not turn out to be a reliable indicator. Measured values depend too strongly on skin texture, on the ambient humidity and temperature. A similar situation exists in relation to other changes in the autonomic nervous system. Pulse and heart rate variability are subject, among other things, to pharmacological influences, as well as to variation due to age, sex and comorbidities. Just like measuring the dilation of pupils, they can serve as a sign of the presence of pain; they are however not suitable for quantitative measurement.

Digitalised agony via EEG

As with imaging methods, reading the specific discharge of pain signals through the EEG has however progressed a relatively long way. In 2011 Leslie Prichep and her colleagues at the Medical College of New York University published a feasibility study for pain determination via brainwave measurement in chronic pain patients. Mathematical calculations led the researchers to the regions on the skull surface with particularly strong significance. The respective EEG data matched images derived by functional magnetic resonance imaging; this data points to the various centres in the brain that are significantly involved in the sensation of pain: the thalamus, somatosensory cortex, anterior and posterior insula, parts of the prefrontal cortex and the cingulum. When pain relief is employed, conductivity from these regions shows a reduction in signal strength.

The knowledge derived by the research group in New York is in the meantime being put to use by one start-up enterprise. PainQx, using the New York researchers’ EEG algorithm licence, wants to be able to offer in as little as a few years an inexpensive pain measurement procedure. The target groups are not only doctors and hospitals, but also nursing homes and retirement homes, where residents are not always able to make their condition known correctly by themselves. The most economical documentation derived from clinical trials should also delight pharmaceutical companies favouring PainQx’s development. A mobile device receives the data and displays the final result; assessment is carried out centrally in a cloud-based data centre.

One publication in 2014 [Paywall] from India reaffirms the hopes of the young company from Philadelphia. It sees in this EEG analysis of certain signals a good way to manage and make adjustments during the anaesthesia procedure. There are still problems to deal with in the conductivity of peripheral brainwaves because the induced potentials are measured at some distance from the event’s point of origin. External influences can thereby easily affect the accuracy of the recorded signals. In contrast to EEG analysis, sensors used in magnetic encephalography measure magnetic fields which arise via intracellular dendritic activity and can thus permit more direct electric conduction. This method is nevertheless technically very complicated and therefore has not yet made it into the hospital routine.

Promising mimic analysis

By using another promising but completely different method, researchers from San Diego are trying to make pain measurable in children. They base their decisions on an automated system that can read emotions from facial expressions: the Facial Action Coding System. 46 different anatomical movement patterns provide this evidence on whether the person is angry, euphoric or pensive. The software, connected to a video camera, can make conclusions about possible pain from movements such as the lowering of the eyebrows, frowning, lifting of the cheeks or a pinching of the mouth. The program is now fast enough to instantaneously display the most current state of mind, while delivering amazingly accurate results. The calculator also exposes faked mood expressions better than do human facial expression analysts.

In the journal “Pediatrics” Jeannie Huang and her colleagues published a study involving 50 children between five and eighteen years of age after a laparoscopic appendix operation. A camera captured the faces of patients at various visits shortly after the procedure and at a follow-up appointment three weeks thereafter. She recorded during these the response to ongoing surgical pain as well as to an immediate pain when pressure was applied to the wound. When compared with the subjective scale of adolescent patients, video technology achieved remarkably good results in both acute and persistent pain. Assessments by nursing staff and parents – both in qualitative and quantitative terms – also served in assessing the optical technical pain measurement capability. Whereas care staff as opposed to parents were good at assessing whether the patient suffered pain during the visits, the parents were better when it came to assessing the extent of pain. Medical personnel often underestimated the pain of patients entrusted to them. The computer image analysis was at least equivalent to the best results from human observers.

Ten year ordeal

It takes on average ten years for specialists to be appropriately able to treat people with a pain disorder. This would make it all the more important, both with acute and chronic pain, to have a suitable diagnostic tool at hand which doctors and nurses can employ in their routine. Great importance is attached to this especially when the patient is unable to inform those in his or her surroundings of his or her state of being. There now exist a number of good approaches which are still awaiting above all else practical testing in the form of large studies. Nobody in this day and age should be waiting for a long time with untreated pain in their hospital bed. As is the situation with treatment methods, there should soon also be some movement on this front with regard to diagnosis.

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